A new approach toward damage localization and quantification of structures under changing temperature condition

William Soo Lon Wah,Yung-Tsang Chen

doi:10.1177/1461348418793079

Abstract

Most damage detection methods developed in the literature cannot give the locations and extent of damages under the presence of varying temperature condition. This is because temperature condition changes the vibration properties of a structure, which are commonly analyzed for damage detection, and temperature gradient throughout the structure makes it difficult to create a baseline for the undamaged structure, as the baseline is generally constructed using features obtained under a wide range of temperature conditions. In this paper, a new insight on how to approach damage detection using only a single temperature condition to create the baseline is proposed. This approach solves the damage detection under changing temperature problem in two stages by first quantifying the change of stiffness of all the elements in a structure due to temperature and damage effects, followed by removing the temperature effect, a global effect, to give the actual damage locations and extent. Using single temperature condition allows new measurements to be compared to a benchmark so that local deviation can be obtained, thus making the damaged elements identifiable. The proposed approach is tested using a beam structure model and a shear building under different gradient temperature conditions, and the results demonstrate that the method successfully eliminates the change in elemental stiffness due to temperature effect and gives correct damage locations and extent. The approach can be implemented with other existing damage detection methods that did not consider the effect of temperature so that structures under varying temperature condition can be analyzed.

Highlights

Engineering structures in general are subjected to constant degradation due to the harsh environmental and operational conditions they are faced with
The difficulties in the development of level 3 damage detection under changing temperature condition may be attributed to the unfit approach adopted by the researchers, as the methods proposed in the literature usually use the concept of creating the baseline of an undamaged structure using damage sensitivity features captured from a wide range of temperature conditions so as to cover all possible scenarios the structure may encounter,[8,20,21] and compare new measurements with the baseline to see whether they lie within the normal range
A new insight on how to approach damage detection of civil engineering structures subjected to varying temperature and to gradient temperature conditions by using a single temperature profile as the baseline is introduced in this paper

Summary

Introduction

Engineering structures in general are subjected to constant degradation due to the harsh environmental and operational conditions they are faced with. The proposed method uses frequency responses, and stiffness and degrees-of-freedom of each element to obtain an extent coefficient for each element to represent the effects of both temperature and damage on the structure. To demonstrate the proposed approach, a beam structure model and a shear building are used as examples for damage detection and quantification, and the results obtained show that by using only one temperature condition for the baseline, damage localization and quantification under gradient temperature condition and nonlinear temperature effect can be achieved. This section introduces the proposed approach for damage detection, localization, and quantification of civil engineering structures subjected to varying temperature condition and to gradient temperature distribution In this approach, damages in a structure are assumed to be represented by reductions in elemental stiffness of the members of the structure, and the locations of the damages are given by the element number each element is assigned to. It should be noted that this way of calculating ct;s for each element allows the proposed method to perform for structures, which have nonlinear temperature gradient across the structure as well as structures whose vibration properties and frequency responses are affected nonlinearly by the changing temperature condition

Summary of the method

Findings

Discussion of the proposed approach

Conclusion